Conventionally, a following method is known for getting a discount at the time of payment by use of electronic coupons accumulated in an IC card. First, a terminal on which contents of an electronic coupon can be displayed is prepared, the contents are looked at by a cashier for confirmation, and discounting is executed. Second, a device by which a paper printed with discount contents of an electronic coupon is outputted is prepared, this paper is read by a cashier through a barcode reader of a POS (Point Of Sale) terminal, and discounting is executed. Third, a device for reading an electronic coupon is connected to a POS terminal to interlocking and discounting is executed.
However, the first method requires human confirmation, thereby making it possible to cause discounting in an illegal manner. The second method allows illegal discounting by copying paper. The third method requires a major change in POS systems.
Also, patent documents similar hereto include Japanese Patent Laid-open No. 2006-23864. However, this patent document has no idea of using existing POS systems.